A novel supply voltage monitor which uses a LED to show the status of a power supply.This simple and slightly odd circuit can clearly show the level of the supply voltage in a larger device as long as the indicator has good 12 volts at its input, LED1 gives steady, uninterrupted (for the naked eye) yellow light.

This digital voltmeter is ideal to use for measuring the output voltage of your DC power supply. It includes a 3.5-digit LED display with a negative voltage indicator. It measures DC voltages from 0 to 199.9V with a resolution of 0.1V. The voltmeter is based on single ICL7107 chip and may be fitted on a small 3cm breadth and 7cm length printed circuit board. The circuit should be supplied with a 5V voltage supply and consumes only around 25mA.

This is a low power voltmeter circuit that can be used with alternative energy systems that run on 12 and 24 volt batteries. The voltmeter is an expanded scale type that indicates small voltage steps over the 10 to 16 volt range for 12 volt batteries and over the 22 to 32 volt range for 24 volt batteries. Power consumption can be as low as 14mw when operated from 12V and 160mw when operated from 24V.

The circuit shown on this page is a reasonably Low Cost and moderately Hi-Tech ammeter for use with DCC systems. The circuit meter output is always has the same polarity regardless of the input polarity. This allows a low cost DC voltmeter to be used to monitor a DCC current.

This circuit is designed to provide an inexpensive way to to create a High Impedance Voltmeter while making use of an inexpensive analog or digital multimeter. The circuit is specifically designed for testing phototransistors when they are used in the circuits shown at this site. It has a very high input impedance that will not "Load Down" the sensor that is being checked.

It measure the voltage on a 12V nominal lead acid rechargeable battery. Lead acid batteries normally spend their working lifetime in the voltage range of 11-15 Volts. This meter circuit was designed to show the voltage range of 10-15V on an analog meter movement, it can be used to show the battery charge state from empty to full.